This invention relates to an improvement to a method of manufacturing a decoration piece of synthetic resin that is adapted to be mainly fitted to an automobile, a bicycle, a motor boat, an OA apparatus, a home use electric appliance, a sporting good, a writing article, a bag, a wear or the like.
JP-B-05-018698, JP-B-07-102620 and JP-B-3235943 disclose methods of manufacturing a three-dimensional decoration piece of synthetic resin such as an emblem, using a metal mold and high frequency dielectric heating.
However, the inventions disclosed in the above JP-B-05-018698 and JP-B-07-102620 employ both a protruding mold and an indented mold. A three-dimensional decoration piece is manufactured between the protruding mold and the indented mold. Thus, the manufactured three-dimensional decoration piece is not flat at the rear surface, but has a recess (hollow) at the rear side. Then, the area of the piece to be bonded or to be made to adhere to the object of mounting, which may be an automobile, is very small. Therefore, such a piece is required to show a strong bonding or sticking effect. Additionally, both the protruding mold and the indented mold are required to be dimensionally highly accurate. The above cited JP-B-3235943 does not disclose any method that employs a protruding mold and a indented mold.
With the manufacturing methods disclosed in the above JP-B-05-018698 and JP-B-07-102620, a three-dimensional pattern is molded in the inside of a fusion cutter which cuts the inner part of the pattern from the outer part. However, the outer part is pulled by the fusion cutter at the time of cutting, so as to make the cutting operation difficult.
Additionally, with the manufacturing methods disclosed in the above JP-B-05-018698 and JP-B-07-102620, a material is pinched between an indented mold and a protruding mold, and the material is pressed by the metal molds. As a protruding mold is used, protrusions and indentations are formed at the rear side of the manufactured three-dimensional decoration piece. Therefore, if a bonding or sticking layer is to be formed on the rear surface of the three-dimensional piece as a lining layer during the manufacturing process, it is not possible to use a sticking material such as a sticky tape for the lining layer. If a thermally adhesive material is used as lining material, the lining material will become flat as it is pressed. Thus, it is not possible to manufacture a three-dimensional decoration piece having an adhesive feature on the rear surface. If such a pattern is manufactured, the effective bonding strength would be low and poor.
Furthermore, with the manufacturing methods disclosed in the above JP-B-05-018698 and JP-B-07-102620, a material is pinched between an indented mold and a protruding mold, and the material is pressed by the metal molds. When a three-dimensional piece is molded directly on a base member that may be a fabric, the base member is also pulled by the indented mold and the protruding mold. Thus, when molding a three-dimensional piece directly on a base member that may typically be a fabric, the base member is required to be extensible. Thus, candidate materials that can be used for the base member are limited to extensible fabrics or the like.
According to any of the inventions disclosed in the above cited patent documents, while it is possible to weld the thermoplastic synthetic resin material from which a three-dimensional piece is molded and a base member that may typically be a fabric, the thermoplastic synthetic resin material is welded to the base member at the parts of the molded product other than the three-dimensional pattern (unnecessary parts). Then, it is difficult to remove the unnecessary parts. The cur surfaces can be coarse ones if the unnecessary parts are removed by cutting.